AUTOMOTIVE ELECTRONICS
UNIT-4
Section-A
1. What is Slot Car?
A slot car (sometimes, slotcar) is a powered miniature auto or other vehicle that is
guided by a groove or slot in the track on which it runs. A pin or blade extends from the
bottom of the car into the slot. Though some slot cars are used to model highway traffic
on scenic layouts, the great majority are used in the competitive hobby of slot car racing
or slot racing.
2. What is the Abbreviation of TCU?
Transmission control unit
3. Whatis TCU?
A transmission control unit or TCU is a device that controls modern electronic
automatic transmissions.
4. What is the use of TCU?
A TCU generally uses sensors from the vehicle as well as data provided by the Engine
Control Unit to calculate how and when to change gears in the vehicle for optimum
performance, fuel economy and shift quality.
5.What is PCM?
Powertrain Control Module
Section-B
1.Explain Brake-by-wire concept?
Drive-by-wire technology in automotive industry replaces the traditional mechanical and
hydraulic control systems with electronic control systems using electromechanical
actuators and human-machine interfaces such as pedal and steering feel emulators.
Brake-by-wire represents the replacement of traditional components such as the pumps,
hoses, fluids, belts and vacuum servos and master cylinders with electronic sensors and
actuators.
Some x-by-wire technologies have been already installed on commercial vehicles such as
steer-by-wire, and throttle-by-wire. Brake-by-wire technology is still under development
by some automobile and automotive parts manufacturers industry worldwide and has not
been widely commercialized yet. This is mainly due to the safety-critical nature of brake
products. So far, Mercedes-Benz (Sensotronic) and Toyota (Electronically Controlled
Brake) already use almost fully brake-by-wire systems, on the Mercedes-Benz E-class
and SL models and on Toyota's Estima.
2.Explain the Architecture of an Electromechanical
Braking System
Fig. 1. General architecture of an EMB system.
General architecture of an electromechanical braking (EMB) system in a drive-by-wire
car is shown in Fig. 1. The system mainly comprises five types of elements:
1.
2.
3.
4.
5.
Processors including an Electronic Control Unit (ECU) and other local processors
Memory (mainly integrated into the ECU)
Sensors
Actuators
Communication network(s).
Once the driver inputs a brake command to the system via a human-machine interface HMI (e.g. the brake pedal), four independent brake commands are generated by the ECU
based on high level brake functions such as anti-lock braking system (ABS) or vehicle
stability control (VSC). These command signals are sent to the four electric calipers (ecalipers) via a communication network. As this network might not be able to properly
communicate with the e-calipers due to network faults, HMI sensory data are also
directly transmitted to each e-caliper via a separate data bus.
In each e-caliper a controller uses the brake command (received from ECU) as a
reference input. The controller provides drive control commands for a power control
module. This module controls three phase drive currents for the brake actuator which is a
permanent magnet DC motor, energised by 42V sources. In addition to tracking its
reference brake command, the caliper controller also controls the position and speed of
the brake actuator. Thus, two sensors are vitally required to measure the position and
speed of the actuator in each e-caliper. Because of the safety critical nature of the
application, even missing a limited number of samples of these sensory data should be
compensated for.
3. Explain the Voting system
Voting
A brake-by-wire system, by nature, is a safety critical system and therefore fault
tolerance is a vitally important characteristic of this system. As a result, a brake-by-wire
system is designed in such way that many of its essential information would be derived
from a variety of sources (sensors) and be handled by more than the bare necessity
hardware. Three main types of redundancy usually exist in a brake-by-wire system:
1. Redundant sensors in safety critical components such as the brake pedal.
2. Redundant copies of some signals that are of particular safety importance such as
displacement and force measurements of the brake pedal copied by multiple
processors in the pedal interface unit.
3. Redundant hardware to perform important processing tasks such as multiple
processors for the electronic control unit (ECU) in Fig. 1.
In order to utilize the existing redundancy, voting algorithms need to be evaluated,
modified and adopted to meet the stringent requirements of a brake-by-wire system.
Reliability, fault tolerance and accuracy are the main targeted outcomes of the voting
techniques that should be developed especially for redundancy resolution inside a brakeby-wire system.
Example of a solution for this problem: A fuzzy voter developed to fuse the information
provided by three sensors devised in a brake pedal design.
4. Explain the Missing data compensation
In a by-wire car, some sensors are safety-critical components, and their failure will
disrupt the vehicle function and endanger human lives. Two examples are the brake pedal
sensors and the wheel speed sensors. The electronic control unit must always be informed
of the driver’s intentions to brake or to stop the vehicle. Therefore, missing the pedal
sensor data is a serious problem for functionality of the vehicle control system. Wheel
speed data are also vital in a brake-by-wire system to avoid skidding. The design of a bywire car should provide safeguards against missing some of the data samples provided by
the safety-critical sensors. Popular solutions are to provide redundant sensors and to
apply a fail-safe mechanism. In addition to a complete sensor loss, the electronic control
unit may also suffer an intermittent (temporary) data loss. For example, sensor data can
sometimes fail to reach the electronic control unit. This may happen due to a temporary
problem with the sensor itself or with the data transmission path. It may also result from
an instantaneous short circuit or disconnection, a communication network fault, or a
sudden increase in noise. In such cases, for a safe operation, the system has to be
compensated for missing data samples.
Example of a solution for this problem: Missing data compensation by a predictive filter.
5. Explain the Accurate estimation of position and speed of brake
actuators in the e-calipers
The caliper controller controls the position and speed of the brake actuator (besides its
main task which is tracking of its reference brake command). Thus, position and speed
sensors are vitally required in each e-caliper and an efficient design of a measurement
mechanism to sense the position and speed of the actuator is required. Recent designs for
brake-by-wire systems use resolvers to provide accurate and continuous measurements
for both absolute position and speed of the rotor of the actuators. Incremental encoders
are relative position sensors and their additive error needs to be calibrated or
compensated for by different methods. Unlike the encoders, resolvers provide two output
signals that always allow the detection of absolute angular position. In addition, they
suppress common mode noise and are especially useful in a noisy environment. Because
of these reasons, resolvers are usually applied for the purpose of position and speed
measurement in brake-by-wire systems. However, nonlinear and robust observers are
required to extract accurate position and speed estimates from the sinusoidal signals
provided by resolvers.
Example of a solution for this problem: A hybrid resolver-to-digital conversion scheme
with guaranteed robust stability and automatic calibration of the resolvers used in an
EMB system
6. Explain the Measurement and/or estimation of clamp force in the
electromechanical calipers
A clamp force sensor is a relatively expensive component in an EMB caliper. The cost is
derived from its high unit value from a supplier, as well as marked production expenses
because of its inclusion. The later emanates from the complex assembly procedures
dealing with small tolerances, as well as on-line calibration for performance variability
from one clamp force sensor to another. The successful use of a clamp force sensor in an
EMB system poses a challenging engineering task. If a clamp force sensor is placed close
to a brake pad, then it will be subjected to severe temperature conditions reaching up to
800 Celsius that will challenge its mechanical integrity. Also temperature drifts must be
compensated for. This situation can be avoided by embedding a clamp force sensor deep
within the caliper. However, embedding this sensor leads to hysteresis that is influenced
by friction between the clamp force sensor and the point of contact of an inner pad with
the rotor. This hysteresis prevents a true clamp force to be measured. Due to the cost
issues and engineering challenges involved with including the clamp force sensor, it
might be desirable to eliminate this component from the EMB system. A potential
opportunity to achieve this presents itself in accurate estimation of the clamp force based
on alternative EMB system sensory measurements leading to the omission of a clamp
force sensor.
Example of a solution for this problem: Clamp force estimation from actuator position
and current measurements using sensor data fusion.
Section-c
1.Explain the Common slot Car
1. The diagram at right shows the wiring of a typical 1:24 or 1:32 slot car setup. Power
for the car's motor is carried by metal strips next to the slot, and is picked up by contacts
alongside the guide flag (a swiveling blade) under the front of the slot car. The voltage is
varied by a resistor in the hand controller. This is a basic circuit, and optional features
such as braking elements or electronic control devices are not shown. Likewise, the car's
frame or chassis has been omitted for clarity.
HO slot cars work on a similar principle, but the current is carried by thin metal rails that
project barely above the track surface and are set farther out from the slot. The car's
electrical contacts, called "pickup shoes", are generally fixed directly to the chassis, and a
round guide pin is often used instead of a swiveling flag.
Today, in all scales, traction magnets are often used to provide downforce to help hold
the car to the track at higher speeds, though some enthusiasts believe magnet-free racing
provides greater challenge and enjoyment and allows the back of the car to slide or "drift"
outward for visual realism.
Common slot car scales
Models of the Ford GT-40, in 1:24, 1:32 and nominal HO scales. Note that the 1960s-era
HO model has been widened to accept the mechanism.
There are three common slotcar scales (sizes): 1:24 scale, 1:32 scale, and so-called HO
size (1:87 to 1:64 scale). These are also commonly written as 1/24, 1/32, 1/87 and 1/64.
Usual pronunciation is "one twenty-fourth," "one thirty-second," and so on, but
sometimes "one to twenty-four," "one to thirty-two," et cetera.
- 1:24 scale cars are built so that 1 unit of length (such as an inch or millimetre) on the
model equals 24 units on the actual car. Thus, a model of a Jaguar XK-E (185" or 4.7 m
overall length) would be 7.7" long (19.6 cm) in 1:24 scale. 1:24 cars require a course so
large as to be impractical for many home enthusiasts, so most serious 1:24 racing is done
at commercial or club tracks.
- 1:32 scale cars are smaller and more suited to home-sized race courses but they are also
widely raced on commercial tracks, in hobby shops or in clubs. This scale is the most
popular in Europe, and is equivalent to the old #1 Gauge (or "standard size") of toy trains.
Our Jaguar XK-E would be about 5.8" (14.7 cm) in 1:32 scale.
- HO-sized cars vary in scale. Because they were marketed as model railroad
accessories, the original small slot cars of the early 1960s roughly approximated either
American/European HO scale (1:87) or British OO scale (1:76). As racing in this size
evolved, the cars were enlarged to take more powerful motors, and today they are closer
to 1:64 in scale; but they still run on track of approximately the same width, and are
generically referred to as HO slot cars. They are not always accurate scale models, since
the proportions of the tiny bodies must often be stretched to accommodate a standard
motor and mechanism. The E-Jaguar scales out to 2.1" (5.3 cm) in 1:87 and 2.9" (7.3 cm)
in 1:64). Though there is HO racing on commercial and shop-tracks, probably most HO
racing occurs on home racetracks.
In addition to the major scales, slot cars have been commercially produced in 1:48 and
1:43 scale, corresponding to O scale model trains. 1:48 cars were promoted briefly in the
1960s, and 1:43 slot car sets are generally marketed today (2007) as children's toys. So
far, there is little organized competition in 1:43, but the scale is gaining some acceptance
among adult hobbyists for its affordability and moderate space requirements. The E-Jag
would be 4.3" (10.9 cm) in 1:43.
2. Explain the Related systems and developments
Digital track (SCX, 1995). Digital technology allows cars to change lanes at crossing
points and passing-lane sections.
A number of technological developments have been tried over the years to overcome the
traditional slot car's limitations. Most lasted only a few years, and are now merely
historical curiosities. Only digital control is currently in production.
Around 1962, AMT's Turnpike system (USA) used multiple electrical pickups within the
slot itself to allow drivers to control, to a limited extent, the steering of special 1:25 cars.
In the late 1960s the Arnold Minimobil system (Germany), also marketed as the
Matchbox Motorway (UK), used a long hidden coil, powered by trackside motors, to
move die-cast or plastic cars down the track via a slot and detachable pin. Cars in
different lanes could race, but cars in the same lane moved at the same speed, separated
by a fixed distance.
In the mid and late 1970s several manufacturers including Aurora, Lionel and Ideal
(USA) introduced slotless racing systems that theoretically allowed cars to pass one
another from the same lane. Most used a system of multiple power rails that allowed one
car to speed up momentarily and move to the outside to pass. Though briefly successful
as toy products, none of these systems worked well enough to be taken up by serious
hobbyists.[24]
In 2004, a number of traditional slot car manufacturers introduced digital control systems,
which enable multiple cars to run in the same lane and to change lanes at certain points
on the course. Digitally-coded signals sent along the power strips allow each car to
respond only to its own controller.
In addition, imaginative manufacturers have used the slot track system to allow the racing
of a variety of unusual things, including motorcycles,[1] boats,[28] airplanes,[29]
spacecraft,[29] horses,[1] fictional and cartoon vehicles,[24] snowmobiles,[24] futuristic
railroad trains,[30] and no doubt many more.
3. Explain the Slot car track
The first sectional slot tracks from Scalextric and VIP were molded rubber and folded
metal, respectively, but modern slot tracks fall into two main categories: plastic tracks
and routed tracks.
Three-lane routed track inspired by the Targa Florio
Plastic Tracks are made from the molded plastic commercial track sections. Sectional
track is inexpensive and easy to work with and the design of the course can be easily
changed. The joints between the sections, however, make a rough running surface,
prompting the derisive term "clickety-clack track." The many electrical connections cause
voltage drop and contribute to more frequent electrical problems. For a permanent setup,
the joints can be filled and smoothed, and the power rails soldered together or even
replaced with continuous strips, but the surface is seldom as smooth as a good routed
track.
Routed Tracks have the entire racecourse made from one or a few pieces of sheet
material (traditionally chipboard or MDF, but sometimes polymer materials) with the
guide-slots and the grooves for the power strips cut directly into the base material using a
router or CNC machining. This provides a smooth and consistent surface, which is
generally preferred for serious competition.
4. Explain the Electrical equipment
Power for most slot car tracks comes from a powerpack. Powerpacks contain a
transformer, which reduces high voltage house current to a safe 12 to 20V (depending on
car type), and usually a rectifier, which changes AC to DC, for cooler running and
simpler motors. High-capacity lead-acid batteries are sometimes used for hobby slot cars.
Toy race sets may use dry cell batteries at 3 to 6 volts.
Types of Slot Car Controllers (L to R, from top) - Telegraph Key, c.1955. Thumb
button, c.1957-1970 (1967 shown). Wheel or Dial Rheostat, c.1959-1965 (Aurora 1963
shown). Carbon Disc Plunger, c.1965-1970 (Aurora). Rheostat Plunger, c.1960-1970
(Cox 1966 shown). Full-Grip Style, c.1962 (Marx). Pistolgrip Rheostat 1965 onward
(Aurora/Russkit 1972 shown). Electronic Controller, 1970s onward.
Controllers ("throttles") vary car speed by modulating the voltage from the powerpack.
They are usually hand-held and attached by wires to the track. Besides speed control,
modern racing controllers usually feature an adjustable "brake", "coast", and "dial-out".
Braking works by temporarily connecting the rails together by a switch (or via a resistor
for reduced braking); this converts the car's motor into a generator, and the magnetic
forces that turned the motor are now slowing it down. Coast allows a certain amount of
power to continue to the track after the driver has "let-off" (which would otherwise cut all
power to the car). A dial-out allows the driver to limit the maximum power that can reach
the car.
The early rail-car tracks used telegraph keys, model-train rheostats and other improvised
means to control car speed. The first commercial race sets (1957) used handheld
controllers with a thumb-button; like the telegraph key, these were either on or off,
requiring the driver to "blip" the throttle for intermediate speeds. Later versions had an
intermediate speed, and one late version used a buzzer mechanism to provide full-range
speed control.
From 1959 to about 1965, most HO slot sets had a table-mounted controller with a
miniature steering wheel or simple dial-knob operating a rheostat (variable resistor),
which gave precise control throughout the car's speed range. This type could be left on a
particular speed setting, making it very suitable for model highway layouts, but they were
awkward for racing. Around 1960, handheld rheostats began to appear. Most early
examples had vertical, thumb-operated plungers with the rheostat in the grip. Aurora had
a plunger design in which a stack of carbon/silicon discs replaced the rheostat. Less
common styles included a horizontal thumb-plunger and a full-grip squeeze controller. In
1965, Russkit introduced the trigger-operated pistolgrip controller. The pistolgrip quickly
became the standard rheostat-controller style both for race sets and serious hobbyists, and
has remained so to the present day. Control is by the index finger, and the heat-generating
rheostat is above the grip for comfort and effective ventilation.
For good response, rheostats must be matched to the particular cars involved. To race
different classes of cars, several controllers with different resistance ratings are often
required. In the 1970s, electronic additions to the rheostat controllers became popular,
which allowed them to be tuned to the particular car being raced. Some modern
electronic controllers dispense with the rheostat altogether, and can be used for all classes
and types of car. Digital slot cars generally use a controller that is trigger operated,
though the rheostat housing is replaced by a slim bulge containing the electronics.
On most tracks, a driver will plug or clip his personal controller to his lane's "driver's
station," which has wired connections to the power source and track rails. Modern
controllers usually require three connections - one to the power terminal of the driver's
station (customarily white), one to the brake terminal (red), and one to the track terminal
(black). Conventional slot car tracks are wired in one of two ways: with the power
terminal connected to the power source positive and the brake terminal negative (called
"positive gate"), or the other way around ("negative gate"). Resistance type controllers
can be used with either positive or negative track wiring, most electronic controllers can
only be used with one or the other, although a few electronic controllers feature a switch
that adapts them for either gate configuration.
Formal Competition
Slot car racing ranges from casual get-togethers at home tracks, using whatever cars the
host makes available, to very serious competitions in which contestants painstakingly
build or modify their own cars for maximum performance and compete in a series of
races culminating in national and world championships. For information on types of
formal competition, racing organizations, standards, etc., see slot car racing.
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